Liu Bo, Gao Jin, Xue Mengyong, Lu Binfu, Ye Chenghui, Liu Jiangmin, Yang Jiasen, Qian Jiale, Xu Xiaoguang, Wang Wenlin, Tao Yulong, Ao Wen
School of Geographical Science, Nantong University, Nantong, 226019, China; State of Environmental Protection Scientific Observation and Research Station for Ecological Environment of Hulun Lake Wetland, Hulunbuir, 021008, China.
School of Environment, Nanjing Normal University, Nanjing, 210023, China.
Environ Pollut. 2023 Feb 15;319:120946. doi: 10.1016/j.envpol.2022.120946. Epub 2022 Dec 24.
Although freshwater lakes are considered to be an important source of greenhouse gas (GHG) emissions, the potential driving mechanisms of such emissions are not well understood, especially in steppe lakes. In this study, the GHG emission characteristics in Hulun Lake Basin, including Hulun Lake, Beier Lake, Wulannuoer Lake, and their surrounding watersheds were investigated. The average methane (CH) and nitrous oxide (NO) emission fluxes released from rivers were 67.84 ± 20.53 and 0.11 ± 0.04 μg m·min, which were larger than those of lakes, with values of 28.60 ± 13.02 and 0.06 ± 0.02 μg m·min, respectively. Conversely, the average carbon dioxide (CO) emission flux from lakes (1816.58 ± 498.98 μg m·min) was higher than that of rivers of (1795.41 ± 670.49 μg m·min). The water in Hulun Lake Basin was rich in organic matter and had a high chemical oxygen demand (COD). Three-dimensional fluorescence combined with a parallel factor analysis (3D-EEM-PARAFAC) demonstrated that the organic matter was composed of four humus types (from Component 1 (C1) to Component 4 (C4)), of which, C1 and C4 were terrestrial humus. The fluorescence index (FI) and humification index (HIX) indicated that the organic matter in the water was mainly imported from exogenous humus. The GHG emission fluxes were negatively correlated with these four components, indicating that GHG emissions were mainly affected by the organic matter source and components, and humus was the most important factor that inhibited GHG emissions in steppe lakes. However, the GHG emission flux was relatively high in some areas of the lake, especially in areas with high nutrient levels or where algal blooms occurred, as evidenced by the significantly positive correlations with total nitrogen (TN), total phosphorous (TP), and chlorophyll-a (chl-a) (p < 0.01). The algae-derived organic matter simulated the decomposition of refractory humus, thus, promoting GHG emissions. These findings are crucial for accurately evaluating the GHG emission fluxes, understanding the carbon cycle, and proposing future management strategies for steppe lakes.
尽管淡水湖被认为是温室气体（GHG）排放的重要来源，但其排放的潜在驱动机制尚未得到充分理解，尤其是在草原湖泊中。在本研究中，对呼伦湖流域（包括呼伦湖、贝尔湖、乌兰诺尔湖及其周边流域）的温室气体排放特征进行了调查。河流释放的甲烷（CH）和一氧化二氮（N₂O）平均排放通量分别为67.84±20.53和0.11±0.04μg m⁻²·min，高于湖泊的排放通量，湖泊的排放通量分别为28.60±13.02和0.06±0.02μg m⁻²·min。相反，湖泊的二氧化碳（CO₂）平均排放通量（1816.58±498.98μg m⁻²·min）高于河流的排放通量（1795.41±670.49μg m⁻²·min）。呼伦湖流域水体富含有机质且化学需氧量（COD）较高。三维荧光结合平行因子分析（3D-EEM-PARAFAC）表明，有机质由四种腐殖质类型（从组分1（C1）到组分4（C4））组成，其中C1和C4为陆地腐殖质。荧光指数（FI）和腐殖化指数（HIX）表明，水体中的有机质主要来自外源腐殖质。温室气体排放通量与这四种组分呈负相关，表明温室气体排放主要受有机质来源和组分的影响，腐殖质是抑制草原湖泊温室气体排放的最重要因素。然而，湖泊某些区域的温室气体排放通量相对较高，特别是在营养水平高或发生藻华的区域，这与总氮（TN）、总磷（TP）和叶绿素a（chl-a）呈显著正相关（p<0.01）证明了这一点。藻类衍生的有机质模拟了难降解腐殖质的分解，从而促进了温室气体排放。这些发现对于准确评估温室气体排放通量、理解碳循环以及提出未来草原湖泊管理策略至关重要。
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